Aqueous fluid filter assembly with aeration mitigation

ABSTRACT

An aqueous fluid filter assembly with aeration mitigation includes a cap, a bowl engaging the cap and defining a filter volume, and a filter element disposed in the filter volume. The filter element is sealed against an interior of the cap and an interior of the bowl to provide an unfiltered volume and a filtered volume. An inlet is in fluid communication with the unfiltered volume and an outlet is in fluid communication with the filtered volume via a pickup section. The pickup section has a pick-up section inlet extending into the filtered volume and an air-metering orifice, wherein the air-metering orifice has a diameter less than 30% of the diameter of the pick-up section inlet and the pick-up section inlet is located below the air-metering orifice.

BACKGROUND

Selective Catalytic Reduction (SCR) is an emissions control technologythat has been widely deployed on diesel engine-powered ground vehiclessince 2010 in the United States of America. SCR is a technology forreducing nitrogen oxide emissions by reacting them with an aqueousammonia or aqueous urea solution in the presence of a catalyst. Theaqueous urea solution is typically referred to as Diesel Exhaust Fluid,also referred to as DEF. DEF has unique properties and it is critical tothe performance of the emissions systems on diesel engine equipmentequipped with SCR.

A typical DEF system includes a DEF storage tank or reservoir, a filter,a pump, such as a positive displacement pump, and an injector. The DEFshould be injected into the exhaust stream of the diesel engine as afine mist. In order to produce the fine mist, the positive displacementpump draws DEF fluid from the reservoir to deliver DEF to the injectorat high pressure. These pumps are prone to failure from debris as smallas 40 microns. For this reason, a DEF filter rated at 40 microns orbetter is typically included on the suction side of the pump between thereservoir and the pump.

Experience in the laboratory and the field has shown that DEF tends toabsorb or otherwise trap air in the fluid. The air may be trapped in thefluid in the form of nano-bubbles, or be dissolved in the DEF accordingto Henry's Law. Without limiting the invention to any particular theoryof how air may be entrained in DEF, it is believed that air may bedissolved into fluid and/or air bubbles created while filing the DEFreservoir, or though agitation while the vehicle is under way, during apurge event, or entrained through other means. This entrained air may bereleased at very inopportune times. Certain environmental conditions canexpedite the release of air from DEF. These conditions include, but arenot limited to, an increase temperature or a decrease in absolutepressure. A pressure decrease will occur when there is an increase inaltitude or when the DEF is being drawn by the suction side of a pump.The released air may then accumulate until a large bubble of air iswithdrawn, for example, from the filter assembly, disrupting injectionpressure in the DEF system.

SUMMARY

An aqueous fluid filter assembly according to one example of the presentinvention includes a cap, a bowl engaging the cap and defining a filtervolume, and a filter element disposed within the filter volume. The bowland filter element may be combined into a spin-on filter cartridge. Thefilter element is sealed against an interior of the cap and an interiorof the bowl to provide an unfiltered volume and a filtered volume. Aninlet is in fluid communication with the unfiltered volume and an outletis in fluid communication with the filtered volume via a pickup section.The pickup section has a pick-up section inlet extending into thefiltered volume and an air-metering orifice, wherein the air-meteringorifice has a diameter less than 30% of the diameter of the pick-upsection inlet and the pick-up section inlet is located below theair-metering orifice. In some examples, the air-metering orifice isabout 0.005 to 0.007 inch.

The filter element may be cylindrical. The filtered volume is defined atleast in part by an interior volume of the filter element. The pick-upsection has a length sufficient to locate the pick-up section inletwithin the interior volume of the filter element to allow foraccumulation of separated air above the pick-up section inlet. A portionof the filtered volume defined by the interior volume of the cap mayprovide a space for air to accumulate above the pick-up section inlet.

In some examples, the interior volume of the cap includes a recess toallow for collection of separated air. The air-metering orifice may belocated in the recess where separated air collects.

In some examples, the fluid filter assembly may further include a heaterelement. In one such example, the pick-up section inlet is locatedalongside the heater element. In another such example, the pick-upsection inlet coaxially encloses the heater element.

In some examples, the fluid filter assembly further includes acompressible member inside the filtered volume to provide for protectionagainst freeze damage.

In another example, an aqueous fluid filter assembly includes a cap, abowl engaging the cap and defining a filter volume, and a filter elementdisposed in the filter volume, the filter element having an interiorvolume, the filter element being sealed against an interior of the capand interior of the bowl, the bowl and an outer surface of the filterelement cooperating to provide an outer unfiltered volume and theinterior volume of the filter element and cap cooperating to provide aninner filtered volume. An inlet is in fluid communication with the outerunfiltered volume and an outlet is in fluid communication with the innerfiltered volume via a pickup section. The pickup section includes apick-up section inlet extending into the filtered volume and anair-metering orifice, wherein a diameter of the air-metering orifice isless than 30% of a diameter of the pick-up section inlet and the pick-upsection inlet is located below the air-metering orifice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a cross section view of a known fluid filter assembly.

FIG. 1 b is a detailed view of a portion of the fluid filter assemblyillustrated in FIG. 1 a.

FIG. 2 is a perspective view of a fluid filter assembly according to oneexample of the present invention.

FIG. 3 a is a cross section view of a fluid filter assembly of FIG. 2 .

FIG. 3 b is a cross section view of a fluid filter assembly of FIGS. 2and 3 a, with additional detail illustrated.

FIG. 4 is a cross section view of a fluid filter assembly according toanother example of the present invention.

DETAILED DESCRIPTION

A known filter assembly 10 typical of those installed on the suctionside of a DEF pump is illustrated in FIG. 1 a , with additional detailshown in FIG. 1 b . The filter 10 has a cap 12, bowl 14, filter element16, heater 18, inlet 20 and outlet 22. The filter element is typicallycylindrical with a hollow cylindrical interior. The ends of the filterelement are sealed against the cap and bottom of the bowl. The bowl andouter cylindrical surface of the filter element 16 cooperate to providean outer, unfiltered volume 24. The interior cylindrical volume of thefilter element, bottom of the bowl and interior of the cap cooperate toprovide an inner filtered volume 26. Fluid enters the inlet and flowsinto the outer unfiltered volume. The fluid passes through the filterelement membrane and into the inner filtered volume. The outlet is influid communication with the top of the filtered volume by way of atube, or an aperture in the tube sufficient for fluid flow, within theportion of filtered volume defined by the inside of the cap 12.

A filter as illustrated in FIGS. 1 a and 1 b maybe prone to air problemsfor at least two reasons. First, the membrane of the filter element mayact as an air barrier. Filter elements are typically rated by particlesizes that they are capable of removing from the fluid. For example, a40 micron filter element will remove particles of 40 microns and largerfrom the fluid being filtered. However, the membranes of 40 micronfilter elements may also prevent entrained air from passing through thefilter element. When this happens, the air accumulates in the outerunfiltered volume, typically at the top of the filter bowl. The aircontinues to accumulate until some, or all, of it is released around thefilter element into the filtered volume, typically in a large “slug” orbubble. The “slug” of air travels to the top of the filtered volume andis withdrawn through the filter outlet tube. Once at the “slug” of airreaches the pump, the fluid pressure at the output of the pump drops,affecting injector operation, which may adversely impact emission systemperformance.

Second, because the filter is on the suction side of the pump, pressurewithin the fluid is lower than ambient pressure, especially in the innerfiltered volume on the “clean” side of the filter element. Lower thanambient pressure promotes the release of air out of the liquid.Additionally, operation of the heater element in cold operatingconditions may release additional dissolved air. Once the air isseparated from the DEF, it tends to rise and collect at the uppersections 28 of the filtered volume in the cap. A large aperture in theoutlet tube allows for proper fluid flow, but also allows air pockets tobe re-introduced into the outlet flow as large “slugs” of air. The largeslugs of air disrupt the pressure output and volume flow of the dosingpump. If the disruptions occur frequently enough the system may registera fault and cause reduced vehicle performance.

An improved aqueous DEF Fluid Filter Assembly 100 is illustrated inFIGS. 2, 3 a and 3 b. The Fluid Filter Assembly 100 comprises a cap 112,bowl 114, filter element 116, heater element 118, inlet 120 and outlet122. The filter element 116 and bowl 114 may be combined in a spin-onfilter cartridge. As in known DEF filters, the filter element 116 may becylindrical with a hollow cylindrical interior volume. The ends of thefilter element are sealed against the cap 112 and the bowl 114. Ends ofthe filter element 116 may seal against planar portions of the cap 112and bowl 114. Additionally, or in lieu of engaging the ends of filterelement 116, raised features 114 a may engage and seal against sidewalls of filter element 116. The bowl and outer cylindrical surface ofthe filter element cooperate to provide an outer unfiltered volume 124.The interior cylindrical volume of the filter element, bottom of thebowl and interior volume of cap cooperate to provide an inner filteredvolume 126. Fluid enters the inlet and flows into the unfiltered volume.The fluid passes through the filter element membrane and into thefiltered volume.

Optionally, a portion of filtered volume 126 may be occupied by acompressible member 128 to provide for protection against freeze damage.As freezing DEF expands, the compressible member 128 compresses reducingexpansion stresses on the cap 112, bowl 114, and filter element 116.

The outlet 122 is coupled to the filtered volume by an air-meteringpick-up section 130. Pick-up section 130 may comprise a pick-up sectioninlet 132 extending into the filtered volume, preferably into a portionof the filtered volume defined by the interior cylindrical volume of thefilter element. The pick-up section 130 has a length dimensioned toallow for accumulation of separated air above the pick-up section inlet132, in the portion of the filtered volume defined by the interiorvolume of the cap and above filter element 116 filtered volume. Thepick-up section 130 incorporates an air-metering orifice 134 above thepick-up section inlet 132 preferably in the portion of the filteredvolume defined by the interior volume of the cap, to remove any air thataccumulates in the interior volume of the cap at a slow, controlledrate.

The removal of air via an air-metering orifice 134 having a smalldiameter opening relative to the pick-up section inlet 132, at alocation in the interior volume that is above the inlet of the pick-upsection inlet 132, significantly reduces the potential for a “slug” ofair large enough to disrupt DEF injector performance to accumulate inthe filtered volume or be passed along to the injector pump. To achievethis, the air metering orifice 134 should be of a diameter insufficientfor the fluid flow requirements for the DEF. For example, a diameter ofthe air metering orifice 134 may be less than 30% of the pick-up sectioninlet 132. In one example, the air-metering orifice 134 is a 0.005 inchto 0.007 inch diameter aperture in pick up section 130. Because featuresin the range of thousands of an inch are not readily reproducible at thescale of the drawings, the air metering orifice 134 is not illustratedin FIG. 3 a , and as illustrated in FIG. 3 b , is not to scale toimprove the visibility of the feature.

Also illustrated in FIG. 3 b is a recess 136 in filter cap 112 toprovide a high point at the top of the filtered volume. Air-meteringorifice 134 is located in this recess. Any separated air in the filteredvolume rises and accumulates in the recess, and therefore in thevicinity of the air-metering orifice 134. This promotes metered removalof the separated air.

The example of FIG. 3 a illustrates that outlet 122 and pick up section130 may compromise a unitary tube shaped with an elbow to turn the pickup section inlet 132 into the filtered volume. Alternatively, the flowpath from pick-up section 130 to outlet 122 may be constructed frommultiple components. Pick up section 130 may be located adjacent toheater element 118. Additionally, a portion of inlet 120 may extendtoward heater element 118 to improve thermal coupling.

Another example is illustrated in FIG. 4 . Elements in common with FIGS.3 a and 3 b have the same reference characters and the same descriptionapplies. In the example of FIG. 4 , the air-metering pick-up section 140comprises a larger diameter pick-up section inlet 132 a that is mountedcoaxially with the heater element 118. Air metering orifice 134 islocated on a smaller diameter tube leading to outlet 122. As in priorexamples, air metering orifice 134 is much smaller in diameter thanpick-up section inlet 132 a. To enhance visibility, the air meteringorifice 134 illustrated in FIG. 4 is not to scale.

In view of the foregoing, an improved fluid filter may comprise a cap, abowl engaging the cap and defining a filter volume, a filter elementdisposed in the filter volume, the filter element being cylindrical witha hollow interior volume, the ends of the filter element being sealedagainst an interior of the cap and bottom interior of the bowl. The bowland outer cylindrical surface of the filter element cooperate to providean outer unfiltered volume. An interior cylindrical volume of the filterelement, bottom of the bowl and interior volume of cap cooperate toprovide an inner filtered volume. An inlet is in fluid communicationwith the unfiltered volume, and an outlet is in fluid communication withthe filtered volume via a pickup section comprising a pick-up sectioninlet extending into the filtered volume and an air-metering orifice,wherein the air-metering orifice is less than 30% of the diameter of aninlet of the pick-up section and the pick-up section inlet is locatedbelow the air-metering orifice. The air-metering orifice may be about0.005 to 0.007 inch.

The length of the pick-up section may be of a length sufficient to allowfor accumulation of separated air above the pick-up section inlet, in aportion of the filtered volume defined by the interior volume of the capand cylindrical interior volume of the filter element. The interiorvolume of the cap may include a recess to allow for collection ofseparated air. The air-metering orifice may be located in the recess.

The filter may include a heater element. The filter may also include acompressible member to provide for protection against freeze damage. Thepick-up section may be located alongside the heater element. The pick-upsection may coaxially enclose the heater element.

1.-17. (canceled)
 18. An aqueous fluid filter assembly, comprising: a bowl defining a filter volume; a filter element disposed in the filter volume, the filter element sealed against an interior of the bowl to provide an unfiltered volume and a filtered volume; an inlet in fluid communication with the unfiltered volume; an outlet in fluid communication with the filtered volume via a pickup section; the pickup section comprising a pick-up section inlet extending into the filtered volume and an air-metering orifice, wherein a diameter of the air-metering orifice is less than 30% of a diameter of the pick-up section inlet and the pick-up section inlet is located below the air-metering orifice; and a compressible member inside the filtered volume, wherein the compressible member is configured to compress upon expansion of freezing diesel exhaust fluid reducing expansion stress on at least one of the bowl and filter element.
 19. The fluid filter assembly of claim 18, wherein the air-metering orifice is about 0.005 to 0.007 inch.
 20. The fluid filter assembly of claim 18, wherein the filtered volume is defined at least in part by an interior volume of the filter element and wherein the pick-up section is configured to locate the pick-up section inlet within the interior volume of the filter element.
 21. The fluid filter assembly of claim 20 further comprising a cap, wherein a portion of the filtered volume which is defined by an interior volume of the cap provides space for air accumulation above the pick-up section inlet.
 22. The fluid filter assembly of claim 18 further comprising a cap, wherein the interior volume of the cap comprises a recess to allow for collection of separated air.
 23. The fluid filter assembly of claim 22, wherein the air-metering orifice is located in the recess.
 24. The fluid filter assembly of claim 18, wherein the fluid filter assembly further comprises a heater element positioned alongside the pick-up section inlet.
 25. The fluid filter assembly of claim 24, wherein pick-up section inlet coaxially encloses the heater element.
 26. The fluid filter assembly of claim 18, wherein the filter element is configured to filter diesel exhaust fluid.
 27. The fluid filter assembly of claim 18, wherein the filter element is cylindrical and is configured to filter diesel exhaust fluid.
 28. The fluid filter assembly of claim 18, wherein the bowl and filter element are combined into a spin-on filter cartridge.
 29. An aqueous fluid filter assembly, comprising: a bowl defining a filter volume; a filter element disposed in the filter volume, the filter element having an interior volume, the filter element being sealed against an interior of the bowl, the bowl and an outer surface of the filter element cooperating to provide an outer unfiltered volume and the interior volume of the filter element to provide an inner filtered volume; an inlet in fluid communication with the outer unfiltered volume; an outlet in fluid communication with the inner filtered volume via a pickup section; the pickup section comprising a pick-up section inlet extending into the filtered volume and an air-metering orifice, wherein a diameter of the air-metering orifice is less than 30% of a diameter of the pick-up section inlet and the pick-up section inlet is located below the air-metering orifice; and a compressible member inside the filtered volume, wherein the compressible member is configured to compress upon expansion of freezing diesel exhaust fluid reducing expansion stress on at least one of the bowl and filter element.
 30. The fluid filter assembly of claim 29, wherein the air-metering orifice is about 0.005 to 0.007 inch.
 31. The fluid filter assembly of claim 29, wherein the pick-up section is configured to locate the pick-up section inlet within the interior volume of the filter element.
 32. The fluid filter assembly of claim 29 further comprising a cap, wherein the interior volume of the cap comprises a recess to allow for collection of separated air and wherein the air-metering orifice is located in the recess.
 33. The fluid filter assembly of claim 29, wherein the bowl and filter element are combined into a spin-on filter cartridge. 